Such a print head is known for example from German Pat. No. 2,704,735 and can for example be constructed so that it contains a plurality of ink ducts which open by their print jet openings at the tip of the print head in a grid-like distribution, by means of which it is possible, with a suitable selective triggering of the respective drive elements, piezoelectric ones for example, with electric voltage pulses in the course of a line-by-line movement of the print head, to record characters on a recording medium such as paper. Here the respective drive element as a result of its triggering with the voltage pulses casues a corresponding pulse-like contraction of the ink ducts, by means of which pressure pulses are exerted on the ink present in the ink ducts, which in turn lead to the detachment of ink droplets at the print jet openings of the ink ducts as well as to their being transferred to the recording medium.
In the known print head an ink reservoir is arranged behind the print head part in such a way that the level of the ink reserve is below the level of the print jet openings. The print jets are supplied with ink from the ink reservoir through capillary action, whereby an ink meniscus is then formed on the respective ink jet openings, which makes possible the later detachment of an ink droplet by the pressure pulse described.
The level of the ink reserve should not be too low below the level of the print jet openings, since then the supplying of the ink ducts and the formation of the ink meniscus on the print jet openings will be impaired, so that it could happen that no further droplet detachment occurs. However, on the other hand the level of the ink should also not be above the level of the print jet openings, since then the ink could run out of the print jet openings.
In consideration of the relationships mentioned above, ink printers are arranged so that their print head prints in a horizontal direction on a recording medium moving in a vertical plane. However there are also application cases of a printer in which the recording medium is arranged not in a vertical plane but in a plane inclined to the vertical, which means that the print head must give off the ink droplets obliquely upward or obliquely downward. For this an arrangement which for example is known from German Pat. No. 2,704,735 must correspondingly be positioned inclined with respect to the vertical, which can cause the level difference between the ink reserve and the print jet openings, which is essentially correct in the horizontal arrangement, to be too great when printing obliquely upwards, so that the printing process is interrupted due to the lack of formation of a meniscus on the print jet openings, or the level of the print jet openings is below the level of the ink reserve in the ink reservoir when printing obliquely downward, so that the ink comes out of the print jet openings continually.